By Kent Traders · Updated 27 October 2026 · 7 min read · UK

A plastic light switch needs no earth connection. A metal one does. Metal light switch earthing catches out people who swap a plastic plate for a Nexus Metal one and expect the same two or three wires to do the job. The plate itself is now a conductor, and it needs somewhere to send a fault.

Does a metal light switch need earthing?

Yes. The reason is simple. If a live conductor touches a metal plate, the plate becomes live. A connected earth conductor gives that fault current a path back to the consumer unit, so the protective device trips instead of the next person touching the plate.

A plastic plate cannot carry that fault, which is why plastic switches get away without an earth. Swap it for metal and the rule changes. The wiring behind the wall has to supply an earth, and you have to connect it.

What BG's instructions say about metal light switch earthing

BG's instruction sheet for its Nexus plate switches is short, and most of it is about earthing. We read the BG plate switch instructions and summarised the relevant points below.

Why a metal plate changes the rules

Older houses often have lighting circuits wired in two-core cable, with no earth conductor at the switch. Plastic switches never needed one, so nobody ran it. Later rewires normally use twin and earth, which carries a bare earth conductor to every switch box.

That difference decides whether a metal plate is simple or a job for a professional. Open the box and look. Is there a bare or sleeved earth conductor, and does it reach the box?

Our Part P guide says a like-for-like switch replacement is not notifiable in England. In our reading, a plastic-to-metal swap is more than like for like, because it adds an earthing requirement. The work must still meet BS 7671 either way.

Which Nexus Metal switches this covers

BG's Nexus Metal switches come in five finishes. The first letters name the finish, and the digits give the function. The earth rules above apply across the range, so the finish does not change them.

Box depth matters just as much as the earth link. BG's manual gives 16mm for profiled one and two gang plates and 25mm for three, four and six gang. Its specification sheet lists 16mm against the 43 code, which conflicts with the manual for three gang, so fit 25mm there. Our NBS12 page says it needs a 16mm metal wall box.

Worked example: a three-switch staircase

Take a staircase with a switch at the bottom, one at the top and one on the landing. Assume the existing plates are plastic and the house has twin and earth wiring. That needs two 2-way switches and one intermediate.

Parts come to £13.47 at our prices on 27 October 2026. The cost that matters is the earth work. That is three boxes, three links and three sleeved conductors, and every one must be right before the circuit goes back on.

1. Isolate the lighting circuit at the consumer unit and prove it dead.
2. Open each box and confirm an earth conductor is present and connected.
3. Sleeve any bare earth wire with green and yellow sleeving.
4. Make the earth link from the back box to the front plate, as BG's sheet requires.
5. Fit the plate, check no earth conductor is trapped, then test continuity before you switch on.

Where metal switch jobs go wrong

Metal switch jobs go wrong in a few predictable ways. Almost all of them come from treating the plate like a plastic one.

• Fitting a metal plate to a box with no earth. This is the big one. Stop and get the circuit checked.
• Leaving bare earth wire unsleeved. BG requires green and yellow sleeving on every bare earth wire.
• Skipping the front plate link. BG says decorative products must have it, so the box terminal alone is not enough.
• Leaving four-lug box lugs standing. Remove the top and bottom lugs or bend them fully back.
• Using a box that is too shallow. A cramped box squashes the conductors and the sleeving.
• Assuming the accessory has an earth terminal. Our NBS12 and NBS13 pages label none, so follow BG's instruction sheet.

What to buy: BG Nexus Metal switches

The Nexus Metal brushed steel collection holds 294 products, all in stock on 27 October 2026. For other switch styles, browse light switches or the fused switches. These six cover switches, sockets and a fan isolator.

The NBS52 spur shows the other side of the story. BG's NBS52 page lists 2 earth terminals and certification to BS 1363 Part 4.

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